Overview

The Retrier class provides a utility for executing actions with retry capabilities. It allows filtering by specific exception types and executing pre-retry actions.

Namespace: Unicorn.Taf.Core.Utility

Behavior

Retry Logic

1. The retrier executes the provided action/function

2. If an exception occurs:
   • It checks if the exception type matches the specified exceptions (if any)
   • If the number of attempts hasn’t been exceeded and exception is retryable, it:
   • Logs a warning message
   • Executes the pre-retry action (if specified)
   • Retries the action
3. If all retry attempts fail or the exception is not retryable, the original exception is thrown

Exception Handling

• If no exceptions are specified using OnExceptions(), all exceptions will trigger a retry
• When exceptions are specified, only those exact types or their subclasses will trigger a retry
• The retrier unwraps TargetInvocationException to access the actual inner exception
• If the inner exception is null, the outer exception is thrown

Usage Examples

Basic Usage - Single Retry

var retrier = new Retrier();
retrier.Execute(() => SomeMethodThatMayFail());

Custom Retry Count

var retrier = new Retrier(3); // Retry up to 3 times
retrier.Execute(() => SomeMethodThatMayFail());

Filtering Specific Exceptions

var retrier = new Retrier(3)
    .OnExceptions(typeof(TimeoutException), typeof(IOException));

retrier.Execute(() => 
{
    // Will only retry on TimeoutException or IOException
    PerformNetworkOperation();
});

Adding Pre-Retry Action

var retrier = new Retrier(3)
    .DoBeforeRetry(() => 
    {
        // Reconnect or cleanup before retry
        ReinitializeConnection();
        ClearCache();
    });

retrier.Execute(() => PerformSensitiveOperation());

Working with Return Values

var retrier = new Retrier(2)
    .OnExceptions(typeof(InvalidOperationException));

string result = retrier.Execute(() => 
{
    return FetchDataFromService();
});

Fluent Configuration

new Retrier(5)
    .OnExceptions(typeof(SqlException), typeof(TimeoutException))
    .DoBeforeRetry(() => LogRetryAttempt())
    .Execute(() => DatabaseQuery());